4 Engineering Steps to 34.1 MPG

Now that the Obama Administration has set the Corporate Average Fuel Economy (CAFE) standard at 34.1 mpg by the year 2016, along with tightening CO2 emissions regulations, the world's automotive engineers can lock in their product plans for the next several years. During the first panel discussion at this year's SAE World Congress, titled "Near-Term Powertrain Solutions—Before 2016," executives from Chrysler, Ford, Honda and Hyundai/Kia discussed how they plan to meet the new criteria. While battery-operated, hybrid and plug-in hybrid powertrains continue to grab most of the headlines, the reality is that electrified technologies will compose only a small percentage of the market in the near to mid-term. Old-school gas–piston engines are likely to remain in use for several more decades, and still have plenty of room for improvement. Barb Samardzich, Ford's VP of global powertrain development, emphasized that efficiency solutions must be affordable. In order to make a tangible difference in overall fuel consumption and greenhouse gas emissions, the technology "has to be [available] in hundreds of thousands or millions of units," Sanardzich said.

Here are some of the technologies and innovations that auto engineers are hoping will bring their fleets up to 34.1 mpg.

Engine Downsizing

The new, downsized, 3.5-liter V6 in Fords F-150.

Exactly what will be required to meet the first phase of regulations boils down to five major elements. The most prominent change consumers will see in the next few years is engine downsizing. By applying technologies like variable valve timing, direct fuel injection and turbocharged gasoline engines (GTDI), automakers will replace current engines with smaller-displacement units without sacrificing performance. Thanks to the charge cooling effect of direct injection and more sophisticated electronic controls, these GTDI engines are not subject to the knock and poor off-boost torque characteristics of older turbos. Samardzich announced that Ford would launch several new GTDI applications before year's end, including a 3.5-liter V6 in the full-size F150 pickup truck, and a 2.0-liter inline Four in the new Explorer. Many other companies will also offer downsized turbo engines.

Transmission Tweaks

Ford's dual clutch gearbox.

An engine's efficiency is largely dependent on the transmission bolted to it. Like the internal combustion engine, the torque converter automatic still has room for improvement. Automakers are rapidly moving to replace older four- and five-speed automatic transmissions with new units of six, seven or even eight gears. Again, more sophisticated electronics, new lock-up clutch mechanisms, internal friction reductions through the use of ball and roller bearings, and new fluids are reducing mechanical losses as torque is transferred through the transmission. An increasing number of vehicles are adopting the dual clutch transmission (DCT). While most of the early dual clutch applications, such as Volkswagen's six-speed DSG-used wet clutches, the newer units are equipped with more efficient dry clutches. Six-speed dry dual-clutch transmissions can boost fuel efficiency by 7 to 9 percent over conventional four-speed automatics. Transmission makers Borg Warner and Getrag both introduced new dual dry-clutch modules that will appear in several vehicles in the near future. Chrysler and Fiat will be launching DCTs in the next year, and Ford will introduce its first North American market dual clutch in the new Fiesta that is launching in the next few weeks. Honda has even introduced a DCT in its VFR1200F motorcycle.

Auto Start/Stop

BMW's start/stop system.

Automatic start/stop is another feature that has become increasingly common. These systems switch off the engine when the vehicle comes to a stop to prevent idling, then automatically refire when the brake pedal is released. Start/stop systems can yield a 5 to 8 percent improvement in efficiency when driving in urban environments. Unfortunately, the methodology of current EPA test cycles does not reflect those benefits. However, the new CO2 emissions limits include some vaguely defined adjustment factors for technology such as more efficient air conditioning systems, and it's possible that these factors could be used to give automakers credit for the installation of automatic start-stop systems.

Weight Reduction

A lighter Hyundai Sonata, without the V6.

Finally, weight reduction will be a major factor in reducing fuel consumption. Over the past several decades, vehicles have become significantly heavier to meet safety regulations and add features. Increased use of lightweight materials such as aluminum, carbon fiber and high-strength steels and new metal-forming techniques are contributing to weight savings. Component supplier Mubea showed off its tailor-rolled steel at the show. Using rollers that move closer and farther apart as the steel moves through them produces sheets of varying thickness. Stamping blanks are then cut from this tailor-rolled sheet, and components such as B-pillars and dashboard beams can be produced that have thickness where needed while reducing material where it's not needed for structural stiffness. The 2012 Ford Focus will use a number of parts made of tailor-rolled steel.

Also contributing to weight reduction is engine downsizing. When Hyundai developed the 2011 Sonata, the company decided early on that it would not offer a V6 engine. By not having to support the mass and size of a V6, Hyundai engineers were able to make the engine bay smaller and reduce the structure. From this it also follows that the brakes and suspension can be lighter. Altogether, Hyundai shaved more than 200 pounds from the new Sonata. According to Samardzich, Ford expects to achieve mass reductions of up to 750 pounds in some vehicles over the coming decade.

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